This invention is related to the field of electromagnetic coupling devices for bus communication.
Electromagnetic coupling devices enable energy to be transferred between components of a system via interacting electric and magnetic fields. These interactions are quantified using coupling coefficients. The capacitive coupling coefficient is the ratio of the per unit length coupling capacitance, Cm, to the geometric mean of the per unit length capacitances of the two coupled lines, C1. Similarly, the inductive coupling coefficient is the ratio of the per unit length mutual inductance, Lm, to the geometric mean of the per unit length inductances of the two coupled lines, L1.
FIG. 1 shows a conventional broadside coupler, where the two broadest faces of two adjacent printed circuit board conductor lines are electromagnetically coupled. FIG. 2 shows an edge coupler, where the narrow faces of two conductors on the same layer are coupled.
Conventional coupling devices suffer from deficiencies in several areas. The coupling devices exhibit significant variations in the capacitive coupling coefficient due to manufacturing tolerances in the line geometry and in the relative position of the two coupled lines (xe2x80x9cx,y,z variationsxe2x80x9d). Furthermore, in common manufacturing practices, the width of conductors is subject to variations of between +/xe2x88x920.5 and +/xe2x88x921.0 mils, the relative alignment of conductor layers within a printed circuit board (PCB) is subject to variations of +/xe2x88x925 mils (x,y axis), the distance between conductor layers can vary by +/xe2x88x922 mils (z axis), and the location of holes for guide pins is subject to +/xe2x88x924 mil variations (x,y axis). Therefore, conventional couplers are too sensitive to misalignment to be used in computer systems.
The present invention addresses these and other deficiencies of conventional couplers.